control joints

huangyhg

control joints
i have seen 2 ways of installing control joints in a slab
1) pour, finish, let setup and cut the joints with a saw
2) pour, and as they are finishing the surface they cut in a grove with a trowel
does it make any difference
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generally, saws are used for larger areas. control joints for small areas, such as sidewalks, are usually tooled in with a "grooving tool".  
pca recommends that the depth of the joint be at least 1/4 of the slab thickness.
the sawcuts give a square edge that can be "supported" by sealant (to prevent breaking off the edge from hard wheel traffic). the grooving tool gives a rounded edge that cannot be "supported" by sealant.
many contractors and engineers prefer the early entry saws like "soff cut". this avoids the problems with cracking occuring before the slab is cut.
i hope this helps!